A mechanical apparatus that performs movements similar to motions of a human being using electrical or magnetic actions is called “robot”. It is said that the word “robot” originates from a word “ROBOTA” (slave machine) in Slavic. Here in Japan, robots began to be popularized at the end of the 1960s. Most of them, however, were industrial robots such as manipulators or transport robots intended for automation and unmanning of manufacturing works in a factory.
Recently, research and development regarding a structure of legged mobile robots and its stable walking control such as pet type robots which copy body mechanisms and motions of animals which perform quadrupedal walking like a dog, a cat or a bear or such as “human-like” or “humanoid” robots which copy body mechanisms and motions of animals which perform bipedal upright walking such as a human being or a monkey have proceeded. Thus, expectation for practical use of the legged mobile robots and its stable walking control has been increasing. Such legged mobile robots are superior in that a flexible walking or traveling operation in moving up and down the stairs or in riding over an obstacle can be achieved although they are disadvantageous in that they are unstable and difficult in posture control and walking control compared with robots of the crawler type.
One of applications of legged mobile robots is a substitute for various difficult works in industrial, manufacturing and like activities. The substitution may be, for example, for maintenance works in atomic power plants, thermal power plants and petrochemical plants, for transporting and assembling works of parts in manufacturing factories or for dangerous works and difficult works such as cleaning of multistoried buildings, salvage in fire cites and like places.
Another application of legged mobile robots is a living-based type, that is, an application for “symbiosis” with human being or “entertainment” rather than working assistance. Robots of the type just described regenerate abundant feeling expressions in fidelity making use of motion mechanisms and the limbs of legged walking animals that have a comparatively high intelligence such as human beings, dogs (pets) or bears. Further, it is demanded for a robot of the type described not only to execute motion patterns inputted in advance merely in fidelity but also to achieve a living responding expression dynamically responding to a word or a behavior (“praise”, “scold”, “tap” or the like) received by a user (or some other robot).
Conventional toy machines have a fixed relationship between a user operation and a responding motion, and it is impossible to change a motion of a toy in accordance with a taste of a user. As a result, the user will soon become tired of the toy that only repeats the same motions. In contrast, an intelligent robot autonomously selects a behavior including dialog and machine body movements, and therefore, can achieve realistic communication at a higher intelligence level. As a result, the user will feel deep love and friendship to the robot.
In a robot or some other realistic dialog system, a behavior is normally selected successively in response to a variation of an external environment through a visual sense or an auditory sense. In another example of a behavior selection mechanism, emotions such as an instinct and a feeling are modeled to manage an internal state of a system, and a behavior is selected in response to a variation of the internal state. Naturally, the internal state of the system varies not only depending upon the external environment but also depending upon development of a selected behavior.
However, examples of situated behavior control wherein a robot integrally discriminates a situation in which the robot is placed such as an external environment and an internal state and selects a behavior based on the discrimination are few.
Here, the internal state may include a factor such as an instinct which corresponds, for example, to an access to the limbic system in a living organism, another factor which can be grasped with an ethological model such as an innate desire or a social desire that corresponds to an access to the brain cortex, a further factor called feeling such as joy, sad, anger or surprise, and so forth.
In conventional intelligent robots and other autonomous dialog type robots, the internal state including such various factors as an instinct and a feeling is all managed collectively and one-dimensionally as “emotion”. In other words, the various factors of the internal state exist in parallel to each other, and a behavior is selected only based on a situation of an external world or an internal state without definite selection criteria.
In conventional systems, all behaviors are present in one dimension for selection and development of a motion, and it is determined which one of the behaviors should be selected. Therefore, as the number of motions increases, the selection becomes complicated and it becomes more difficult to perform behavior selection on which a situation or an internal state at the time is reflected.